Grass trimmer sharpening device

ABSTRACT

A portable, powered grass or hedge trimmer or the like comprising a housing enclosing a motor and having a handle and trigger means disposed thereon. A plurality of relatively movable blades are provided, and at least one blade is driven by the motor. The blades include cooperable teeth adapted to cut grass or the like. A novel sharpening device is provided and includes a body or sheath provided with abrasive stones adapted to sharpen the teeth of at least one blade when the motor is energized and the blades moved relative to one another. The sheath, when in place, can also protect one or more of the blades and thereby helps prevent accidental injury when the device is not in use.

ilnited States Patent Weber et al.

GRASS TRIMMER SHARPENING DEVICE Inventors: Edwin]. Weber, Baltimore;Gerald J. Sesta, Glenarm, both of Md.

Black and Decker Manufacturing Company, Towson, Md.

Filed: Feb. 23, 1972 Appl. No.: 228,564

Assignee:

9/1931 Bennettetal .51/211 RX 12/1943 Wisterman et al 30/138 X 2,895,2687/1959 Martinmaas, .lr. 5l/250 Primary Examiner-Donald G. KellyAssistant Examiner-Howard N. Goldberg Att0rney-Leonard Bloom et al.

[57] ABSTRACT A portable, powered grass or hedge trimmer or the likecomprising a housing enclosing a motor and having a handle and triggermeans disposed thereon. A plurality of relatively movable blades areprovided, and at least one blade is driven by the motor. The bladesinclude cooperable teeth adapted to cut grass or the like. A novelsharpening device is provided and includes a body or sheath providedwith abrasive stones adapted to sharpen the teeth of at least one bladewhen the motor is energized and the blades moved relative to oneanother. The sheath, when in place, can also protect one or more of theblades and thereby helps prevent accidental injurywhen the device is notin use. i

7 Claims, 8 Drawing Figures GRASS TRIMMER SHARPENING DEVICE SUMMARY OFTHE INVENTION The present invention is directed to a novel sharpeningdevice for a portable cutting or trimming unit of the type havingrelatively movable, toothed blades and to a novel method of in placesharpening of one or more blades of this type of unit. This deviceincludes a sheath or body provided with abrasive means engageable withcutting teeth on at least one of the blades of the unit. Sharpening iseffected simply by relatively moving the blades, as by turning the uniton, with the sheath in place, and requires no disassembly of the bladesfrom the unit. Sharpening is, therefore, carried out simply and quicklyand, since no direct handling of the blades is required, is performedvery safely. Furthermore, the sharpening device can be constructed toprotectively encompass one or more blades when in place thereon toreduce the likelihood of injury to one handling the unit, or to theblades themselves, while the unit is not in use.

Main-objects, therefore, of the present invention are to provide a novelsharpening device and method for one or more toothed blades of aportable,- powered, cutter or trimmer unit or the like, which device isadapted for quick, easy, and safe use, and which does not requiredisassembly of the blade or blades from the unit for sharpening.

Further important objects of the present invention are to provide atoothed blade sharpening device of the above character which can alsoserve as a storage and safety device to protect one or more of theblades from being damaged, or from injuring one handling the unit, whennot in use.

Additional important objects are to provide a novel blade sharpeningdevice of the above character which is relatively inexpensive tomanufacture, durable in construction, and reliable in use. i

Other important objects to the present invention will become moreapparent from a consideration of the detailed description to followtaken in conjunction with the drawings annexed hereto.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspectiveview-illustrating-a portable, power driven grass trimmer and a bladesharpening device therefor embodying the present invention;

FIG. 2 is an enlarged plan view of the blades and the sharpening deviceof FIG. 1 and showing the parts in position for blade sharpening; I

FIG. 3 is a plan view of the sharpening device of FIGS. 1 and 2;

FIG. 4 is a sectional view of FIG. 3 taken lines 4-4 thereof;

FIG. 5 is a sectional view of FIG. 2 taken along the lines 55 thereof;

FIG. 6 is an enlarged sectional view of a portion of FIG. 3 taken alongthe lines 66 thereof;

FIG. 7 is a perspective view illustrating one modified form of theinvention as used with a different type of cutter or trimmer unit; and

FIG. 8 is a sectional view of FIG. 7 taken along the lines 8-8 thereof.

BROAD STATEMENT OF THE INVENTION Broadly described, the presentinvention relates to a sharpener for a cutting blade assembly includingrelaalong the tively movable toothed cutting blades, said sharpenercomprising a body, said body including means detachably securing saidbody to one of said blades, spaced abrasive means on said body fittingbetween the teeth of said one blade and rubbingly engaging the teeth ofthe other of said blades when said body is detachably secured to saidone blade, said abrasive means functioning to sharpen the teeth of saidother blade when it is moved relatively to said one blade.

In another aspect, the present invention relates to a sharpener for aportable power operated cutter of the type having at least tworelatively movable toothed cutting blades, said sharpener comprising abody having a blade receiving recess therein, said body havingupstanding side walls including a tapered portion adapted to grippinglyengage one of said cutting blades when the latter are in position insaid recess, a plurality of abrasive stones fixed in said recess andadapted to interfit between the teeth of said one cutting blade, saidstones adapted to engage the underside of the teeth of the other of saidcutting blades and sharpen the latter when the blades are moved relativeto each other, said side walls of said body being shaped to allow manualinsertion and removal of said blades to and from said body recess. I Instill another aspect, the present invention relates to a sharpener for acutting bladeassembly of a portable grass trimmer or the like of thetype including a housing having a handle, a motor in said housing andhaving an output shaft, stationary toothed blade means fixed to saidhousing, movable toothed blade means driven by said output shaft andcooperable with said stationary blade means, said sharpener comprising abody, means on said body releasably engageable with said stationaryblade means to releasably secure said body thereto, a pluiality ofabrasive stones fixed to said body and extending between the teeth ofsaid stationary blade means and engaging the teeth of said movableblade-means when said body is releasably engaged with said stationaryblade means, the teeth of said movable blade rubbingly engaging saidabrasive stones when said body is engaged with said stationary blademeans and said motor is energized and said movable blade means driven bysaid output shaft, whereby said movable blade means is sharpened.

In still another aspect, thepresent invention relates to a sharpener fora cutting blade assembly of a portable trimmer or the like of the typeincluding a housing having a handle, a motor in said housing, astationary blade fixed to said housing and having spaced teeth thereon,amovable blade operatively engaged with said motor and having spacedteeth thereon, said stationary blade teeth and said movableblade teethhaving cooperatively engageable shearing .edges thereon, said sharpenercomprising a body including means grippingly engageable with saidstationary blade, spaced abrasive means on said body fitting between theteeth of said stationary blade and rubbingly engaging the teeth of saidmovable blade when said body is grippingly engaged with said stationaryblade, said abrasive means functioning to sharpen the shearing edges ofthe teeth of said movable blade when it is driven by said motor.

DETAILED DESCRIPTION Referring now more specifically to the drawings, aportable, power operated grass trimmer, one type of unit with which thepresent invention finds particular use, is illustrated generally at 11in FIG. 1 and is seen to include a clam shell housing 1-3 having a motorportion 15, a transmission portion 17 and a handle '19. An electricmotor (not shown) is disclosed within the motor portion 15 and may bepowered from a suitable electric source connected thereto by a line cord(not shown). Alternatively, the motor may be powered by electric storagebattery means suitably located within the housing 13. A switch trigger21, disposed within the handle 19, turns the motor on and off. A safetylock assembly 23 interlocked with the trigger 21, is provided atop thehandle .19 to prevent accidental actuation of the motor.

It will be understood that the particular blade means of cutting ortrimming units of the general category with which the present inventionfinds use is not limited -to that illustrated herein and describedbelow. Thus,

the blade means may include: one or more stationary blades together withone or more movable blades; a plurality of blades all of which move;.ormovingblades which oscillate, rotate, reciprocate, or a variationthereof. In addition, the description of toothed cutting blades tofollow refers generally to blades having cooperable shearing edgesdisposed non-parallel or nonconcentric to the path of relative blademovement. Furthermore, the terms cutting (cutter) or trimming (trimmer)unit refer to devices of this general type used to cut grass, shrubs-orfoilage, or a variety of other similar or related materials.

Withthis in mind, the illustrated trimmer is, provided with a pair ofgrass cutting blades 24,25 which extend forwardly from the housingportion 17. The bottom blade 24 is fixed to the housing-13 and isprovided .with a plurality of spaced, generally forwardly extendingteeth 27. The upper blade 25, on the other hand, is pivoted to the fixedblade 24 by means of a rivet. 29, and also has a plurality of forwardlyextending, spaced teeth 31. The blade 25 is oscillated about the pivot29 by means offthe motor (not shown) disposed within the housingportion.15 by, for example, an orbiting eccentric driven by the motor anddisposedwithin an elongated slot (not shown) in the rearward,concealedportion of the blade 25. Such constructions are relativelycommon and well known in the art and need not be explained further here.i I

Desirably, the stationary blade 24 is somewhat wider than theoscillating blade 25'and has one more tooth than the blade 25. Inaddition, the stroke ofthe oscillating blade 25 is 'such that cuttingedges 33 on each tooth 31 cooperates with cutting edges 35 on each oftwo adjacent teeth 27 on the stationary blade 24, while not extendinglaterally past the confines of the blade 24. Thus, cutting edges 33, 35cooperate with 'one another during relative movement to cut grass orother material disposed therebetween.

In order for the blades 24, 25 to cut properly, their edges 35, 33 mustbe maintained relatively sharp. In addition, in the case of batterypowered devices, blade sharpness controls cutting efficiency of the unitanddirectly affects the life of the batteries. In practice, it has beenfound that in two-bladed shears such as that illustrated herein, thiscan best be achieved by utilizing blades of different hardness, namely,one relatively hard, permanently sharpened blade, and one of somewhatless hardness. Blades of the same or nearly the same hardness tend towear excessively, especially where the blades are held in scissor-likeengagement. Thus, if the dulled blades cannot be resharpened, they mustbe replaced.

Specifically, then, the stationary blade 24 desirably is constructedfrom arelatively hard and wear resistant material, such as heat treatedsteel, and its edges'35 are initially sharpened at a suitable angle, forexample perperidicular to the plane of the blade 24 The moving blade 25,on the other hand, is constructed from, for example, a heat treatedsteel which is softer'than the material of the blade 24. The edges 33 ofblade 25 are also initially sharpened at a suitable, forexample, anacute angle; however, as a result of thesofter nature of the material ofthe blade 25, the edges 33 require periodic sharpening during use inorder to maximize the cutting efficiency of the device. Propersharpening of these blades, however, can be difiicult and often requiresa professional to perform it properly; Quite often, it also is necessaryto remove one or both blades from units of this type in order to performthis sharpening. This is undesirable for obvious reasons which includeexpenditure of time and money to maintain the tool 11 inoptimum'operating condition.

In accordance with the present invention, the edges 33 of blade 25 arequickly and easily sharpened by the user without-requiring anyspecialskill or tools and without requiring-any disassembly of the blade fromthe unit. Thesharpener assembly of the present invention comprises aplastic body 41 having a hollow recess 43 formed therein. The body 41 ispreferably constructed from astitf, non-warping, slightly flexibleplastic material, such as .those sold.-under the trademarks .ABS, Nylonor Lexan. The recess 43 is shaped somewhat complementary to ,the outsidecontour of the blade 24 and is adapted to snugly receive the bladetherein. Preferably. the-body 41 defines overhanging lips' 45, 47 whichoverlay the outer edges of the blade 24 at least at an area adjacent thetool housing 17. Thus, when inserting the blade 24 into the recess 43,the blade s outer edges snap? under theoverhanging jlips 45, 47, tothereby retain the blade 24 in place within the recess 43. ;When it isdesiredto remove the body 41 from the blade 24, the body 41 simply ispried away from the blade 24, 'and. the flexible nature of the materialof the body 41. allows thelips 45, 47 to deflect outwardly to therebyrelease the blade 24. In addition, the body 41 may have recesses 46, 48to receive the end of the outer teeth '27 on the blade 24 to help retainto the blades 24, 25 in place on the body .41.

A plurality of abrasive sharpening members, for example, abrasive stonesare disposed within the recess 43 in the body 41 and are suitablydisposed so that when the stationary blade 24 is positioned in therecess 43 and the tool ll-turned on, the blade 25 is sharpened. Thestones 51 are positioned to fit between the teeth 27 of the stationaryblade 24 and protrude slightly upwardly thereof. The teeth 31 of themoving blade 25 are normally disposed in rubbing contact with the teeth27 of the stationary blade 24 so that when the blade 24 is positionedwithin the recess 43, the teeth 31 of the moving blade 25 resilientlyengage the abrasive stones 51. Thus, with the parts so positioned, thecutting edges 33 ofthe teeth 31 rub against the stones 51 when the tool11 is turned on.

By way of example, the stones 51 can be constructed of an aluminum oxidevitreous material having a coarseness of approximately grit. With thismaterial, and utilizing a heat treated steel for the movable blade 25,the stone crystals break away as the blade teeth 31 rub thereagainst.This results in sharp edges on the stones 51 being continuouslypresented to the blade edges 33.

The stones 51 are secured in place within the body recess 43 in anysuitable manner. For example, the body 41 may be provided with molded inrecesses 53 and the stones 51 secured in place within the recesses 53 bya suitable rubber based cement or a melting type glue.

A modified form of the invention is shown in FIGS. 7 and 8. Here, thetool with which the sharpening device is used as a power operated hedgetrimmer and having an elongated stationary blade or comb 101 and areciprocating blade 103. The comb 101 has laterally extending, spacedteeth 105 disposed on one or both sides thereof. The reciprocatingblade, conventionally operated by a rotating crank (not shown) driven byan electric motor (not shown) is provided with corresponding laterallyextending, longitudinally spaced treading teeth 107 on one or both sidesthereof. A cover plate 109 is disposed atop the reciprocating blade 103and, together with the stationary blade 101, sandwiches thereciprocating blade 103 therebetween. Hedge trimmer construction of thistype, whether driven by a corded electric motor or a cordless electricmotor are well known in the art and need not be explained further here.However, for a detailed explanation thereof, reference may be made tothe US. Pat. to Wells, No. 3,564,714 and the U.S. Pat. to Riley, No.3,161,954, both of which are owned by the assignee hereof.

A sharpener device for sharpening the cutting edges of the teeth 107 ofthe reciprocating blade 103 is illustrated generally at 111 in 'FIGS. 7and 8 and is seen to include a resilient sheath 113 adapted toreleasably grip the underside of the stationary blade 101 and the top ofthe blade cover plate 107. The resilient holder 113 is provided with one'or more abrasive stones 115 adapted, when the holder 113 is in place asshown in FlGS. 7 and 8, to fit between adjacent ones of the teeth 105 ofthe stationary comb 101. When so positioned, the abrasive stones 115rubbingly engage the underside of the cutting teeth 107 of the blade103, so that these teeth 107 may be sharpened simply by turning thedevice on and reciprocating the blade 103 with the resilient holder 113in place.

By the foregoing, there has been disclosed a novel sharpening devicecalculated to fulfill the inventive objects hereinabove set forth, andwhile preferred embodiments of the present invention has beenillustrated and described in detail, various additions, substitutions,modifications, and omissions may be made thereto without departure fromthe spirit of the invention.

We claim:

1. A sharpener for a cutting blade assembly including relatively movabletoothed cutting blades, said sharpener comprising a body, said bodyincluding means detachably securing said body to one of said blades,spaced abrasive means on said body fitting between the teeth of said oneblade and rubbingly engaging the teeth of the other of said blades whensaid body is detachably secured to said one blade, said abrasive meansfunctioning to sharpen the teeth of said other blade when it is movedrelatively to said one blade.

2. A sharpener for a portable power operated cutter of the type havingat least two relatively movable toothed cutting blades,'said sharpenercomprising a body having a blade receiving recess therein, said bodyhaving upstanding side walls including a tapered por tion adapted togrippingly engage one of said cutting blades when the latter are inposition in said recess, a plurality of abrasive stones fixed in saidrecess and adapted to interfit between the teeth of said one cuttingblade, said stones adapted to engage the underside of the teeth of theother of said cutting blades and sharpen the latter when the blades aremoved relative to each other, said side walls of said body being shapedto allow manual insertion and removal of said blades to and from saidbody recess.

3. A sharpener as defined in claim 2 wherein said side wall taperedportions are defiectable to releasably receive said one cutting blade.

4. A sharpener as defined in claim 2 wherein said body recess has adepth, defined by said side walls, greater than the combined thicknessof said blades, whereby said sharpener body effectively protects saidblades. 1

5. A sharpener for a cutting blade assembly of a portable grass trimmeror the like of the type including a housing having a handle, a motor insaid housing and having an output shaft, stationary toothed blade meansfixed to said housing, movable toothed blade means driven by said outputshaft and cooperable with said stationary blade means, said sharpenercomprising a body, means on said body releasably engageable with saidstationary blade means to releasably secure said body thereto, aplurality of abrasive stones fixed to said body and extending betweenthe teeth of said stationary blade means and engaging the teeth of saidmovable blade means when said body is releasably engaged with saidstationary blade means, the teeth of said movable balde rubbinglyengaging said abrasive stones when said body is engaged with saidstationary blade means and said motor is energized and said movableblade means driven by said output shaft, whereby said movable blademeans is sharpened.

6. The improvement of claim 5 wherein said body includes a recess shapedto receive said stationary blade means, means in said recess forgrippingly engaging said stationary blade means, said abrasive stonesbeing positioned in said recess.

7. A sharpener for a cutting blade assembly of a portable trimmer or thelike of the type including a housing having a handle, a motor in saidhousing, a stationary blade fixed to said housing and having spacedteeth thereon, a movable blade operatively engaged with said motor andhaving spaced teeth thereon, said stationary blade teeth and saidmovable blade teeth having cooperatively engageable shearing edgesthereon, said sharpener comprising a body including means grippinglyengageable with said stationary blade, spaced abrasive means on saidbody fitting between the teeth of said stationary blade and rubbinglyengaging the teeth of said movable blade when said body is grippinglyengaged with said stationary blade, said abrasive means functioning tosharpen the shearing edges of the teeth of said movable blade when it isdriven by said

1. A sharpener for a cutting blade assembly including relatively movabletoothed cutting blades, said sharpener comprising a body, said bodyincluding means detachably securing said body to one of said blades,spaced abrasive means on said body fitting between the teeth of said oneblade and rubbingly engaging the teeth of the other of said blades whensaid body is detachably secured to said one blade, said abrasive meansfunctioning to sharpen the teeth of said other blade when it is movedrelatively to said one blade.
 2. A sharpener for a portable poweroperated cutter of the type having at least two relatively movabletoothed cutting blades, said sharpener comprising a body having a bladereceiving recess therein, said body having upstanding side wallsincluding a tapered portion adapted to grippingly engage one of saidcutting blades when the latter are in position in said recess, aplurality of abrasive stones fixed in said recess and adapted tointerfit between the teeth of said one cutting blade, said stonesadapted to engage the underside of the teeth of the other of saidcutting blades and sharpen the latter when the blades are moved relativeto each other, said side walls of said body being shaped to allow manualinsertion and removal of said blades to and from said body recess.
 3. Asharpener as defined in claim 2 wherein said side wall tapered portionsare deflectable to releasably receive said one cutting blade.
 4. Asharpener as defined in claim 2 wherein said body recess has a depth,defined by said side walls, greater than the combined thickness of saidblades, whereby said sharpener body effectively protects said blades. 5.A sharpener for a cutting blade assembly of a portable grass trimmer orthe like of the type including a housing having a handle, a motor insaid housing and having an output shaft, stationary toothed blade meansfixed to said housing, movable toothed blade means driven by said outputshaft and cooperable with said stationary blade means, said sharpenercomprising a body, means on said body releasably engageable with saidstationary blade means to releasably secure said body thereto, aplurality of abrasive stones fixed to said body and extending betweenthe teeth of said stationary Blade means and engaging the teeth of saidmovable blade means when said body is releasably engaged with saidstationary blade means, the teeth of said movable blade rubbinglyengaging said abrasive stones when said body is engaged with saidstationary blade means and said motor is energized and said movableblade means driven by said output shaft, whereby said movable blademeans is sharpened.
 6. The improvement of claim 5 wherein said bodyincludes a recess shaped to receive said stationary blade means, meansin said recess for grippingly engaging said stationary blade means, saidabrasive stones being positioned in said recess.
 7. A sharpener for acutting blade assembly of a portable trimmer or the like of the typeincluding a housing having a handle, a motor in said housing, astationary blade fixed to said housing and having spaced teeth thereon,a movable blade operatively engaged with said motor and having spacedteeth thereon, said stationary blade teeth and said movable blade teethhaving cooperatively engageable shearing edges thereon, said sharpenercomprising a body including means grippingly engageable with saidstationary blade, spaced abrasive means on said body fitting between theteeth of said stationary blade and rubbingly engaging the teeth of saidmovable blade when said body is grippingly engaged with said stationaryblade, said abrasive means functioning to sharpen the shearing edges ofthe teeth of said movable blade when it is driven by said motor.